Crooker fiber optical sensor is light intensity modulation sensor and has got good application. The sensitivity, precision and stability of the sensor are mainly decided by the stability of output power of light source. The electro optical compensation is used to decrease the unstability of light source power by leading in to reference light. We suggested to stable the output power of light source by using the bistable optical device and used this new device to measure the forced force of comb structure. This paper introduced the principle of the device, gived the expermental result and pointed out the new research direction.